This invention relates to telecommunications networks, and more particularly, to line interface units interconnecting customer premises equipment and subscriber lines to such telecommunications networks.
The information age has ushered in an explosive growth of data networking systems, as evidenced by the popularity of the Internet. It is consumer demand for accurate information delivered substantially instantaneously that is the impetus for an evolution of the types of service offered by telecommunications service providers.
Although the traditional provider of telecommunications services is a regional Bell operating company (also known as an RBOC), modem day telecommunications service providers can take various forms. For example, an Internet service provider may provide telephone service and act as a portal for subscriber access to various data networks. Regardless of the identity of the telecommunications service provider, access to customer premises equipment via a subscriber line is critical. Line interface units (or line cards) are the interface between a subscriber line and the serving telecommunications equipment.
All line cards provide basic functions such as battery feed, overvoltage, ringing, supervision, coder/decoder circuit (known as CODEC), hybrid and testing (known as the BORSCHT function). However, supplemental line card functions are required, depending upon the service standard with which the subscriber loop operates. Traditional analog service (i.e., plain old telephone service or xe2x80x9cPOTSxe2x80x9d) is quickly becoming an anomaly in a sea of sophisticated subscriber loop standards such as ISDN, coin, HDSL, ADSL, VDSL, SDSL and 10 base T. Currently, telecommunications service providers operating switches or loop carriers require many different types of line cards for supporting the various types of subscriber loop standards available.
Supporting a plurality of line card types leads to operational difficulties including reduced efficiency of switch terminations, stockpiling of inventory and increased costs associated with moving subscriber lines among the different types of line cards when a service change is requested. For example, if a telecommunications service subscriber wishes to upgrade from POTS to a more advanced type of service, such as ISDN, a technician must physically access the subscriber""s line card to upgrade circuitry or switch the subscriber line termination to an ISDN-capable line card. Manual upgrading of line cards is time consuming and labor intensive. With anticipated increases in subscriber requests for more sophisticated service, it is likely that significant service provider resources continue to be occupied with line card upgrade activities.
The need for a more robust and adaptable line card architecture is recognized and a technological advance is achieved in the telecommunications art by a universal telecommunications line card for serving various types of subscriber loop standards. More particularly, the universal line card design employs a core circuit comprising a high performance CODEC and digital signal processor for allowing selective configuration of the line card interface for serving a subset of a plurality of subscriber loop standards.
The core circuit of the line card interfaces with the metallic twisted pair of the subscriber loop. This interface is connected to the codec circuit which performs analog to digital (and digital to analog) conversions. The codec is also interconnected to a digital signal processor initialized with different algorithms for serving a variety of subscriber loop standards. The digital signal processor is interconnected to a telecommunications network and is capable of passing signals as either timeslots or packets. The core circuit performs all BORSCHT functions required by all subscriber loop standards. Some line cards may also be able to support special high current pulses for operating coin phones and other ""specialized telemetry. All the universal line cards include variable termination impedance matching networks for providing the different line characteristics required by the different subscriber loop standards. When implementing a particular standard format, some functions on the universal line card are disabled so as not to interfere with transmission.
Advantageously, the universal line card is configurable to accommodate various bandwidth, feature and range requirements of an individual subscriber line. For example, POTS can be combined with ISDN and ADSL services on the same line card. Further, the line card can be configured via a remote system so that the need for a technician to upgrade line card services is no longer required.